The Muslims were able to gain power, though, and after a series of successful battles led by Arabs, Turks and Afghans in the early years of the 12th century, they established the Delhi Sultanate, a broad term used to identify this period of Muslim dynasties. At first they were only able to control northern India but later dynasties were able to go deep into central India and even into southern India during the Moghul Empire. Muslim missionaries gained masses of converts preaching during the Crusades.

Weegy: The Byzantine Empire, much like the Roman Empire, faced a formidable array of external enemies. However, it was largely internal decay which destroyed both empires. The political and economic stability of the empire by 1000 A.D. [ led to two lines of development which combined to trigger a pair of interlocking feedback cycles that, in turn, eventually wrecked the empire. First of all, there was the free peasantry upon which the government depended for taxes and recruits. When the empire had been under constant attack, land had been a poor investment. But once stability started to return in the eighth century, many nobles looked greedily upon the farmlands controlled by the free peasantry. There was a constant battle as the nobles tried to get these lands and enserf the peasants. The government, seeing the free peasantry as the backbone of its economy and defence, did what it could to defend them. Basil II in particular fought long and hard to defend the peasants, but even he was unable to break the power of the nobles.
Secondly, and unfortunately for the peasants, not all emperors were strong or even concerned enough to defend the peasants. This was especially true after Basil II's death in 1025 when the empire was at its height and a strong military seemed less necessary. Therefore, a series of weak rulers with little military experience succeeded Basil. During hard times, such as famine, nobles would take the chance to dispossess the peasants. This wouild lead to the decline of the free peasantry and army, which in turn forced the state to rely more and more on expensive foreign mercenaries. This further increased the tax burden on the peasants, which caused more of them to lose their lands, leading to more reliance on mercenaries and so on. ] (More)